At the end of World War II major building of the highway system we know today began in both the U.S. and Europe. In that era brightness of electric lamps was rated the same as commonly used today for the consumer, namely higher wattage produces higher brightness. It is important to understand that “brightness” is related to response of the human eye in the visible part of the spectrum which lies between the shorter wavelengths of ultraviolet and the longer wavelengths of infrared.
Freeways known today in the U.S. were only beginning to be built after the war;
therefore, nighttime road illumination was related to stopping safety in combination with close passing oncoming traffic. Therefore, for visibility safety the Department of Transportation (DOT) established vehicle headlamp wattage to be a maximum of 60 watts on the mainly two-way U.S. roads. In Europe of that reconstruction era the building of higher-speed roadways dictated vehicle headlamps at a maximum 65 watts for visibility safety. Those wattages remain in effect today.
In the mid to late 1990′s technology for manufacturing electric arc type headlamps evolved in Europe. These vehicle arc lamps produce approximately three times the brightness of incandescent vehicle lamps, and arc lamp power consumption is one half the incandescent wattage. Combining those statistics results in a total efficiency improvement approximately six times that of incandescent lamps in the visible spectrum. Under these circumstances 35-watt electric arc lamps readily meet highway regulatory maximum wattage requirements both in the U.S. and Europe, even though they are much brighter to the eye! While that increased brightness is an improvement in night vision for drivers using arc lamps, at the same time there is a major risk of causing unsafe blindness in the oncoming traffic. Clearly there exists an ongoing nighttime vehicle headlamp lighting safety issue.
In order to establish nighttime road safety for both arc and incandescent sources
DOT established sharp headlamp beam pattern regulations. It is now required that the beam pattern top be accurately aimed to relatively strict standards by vehicle manufacturers.
Vehicle headlamp alignment requires significant quality control to assure meeting
DOT aiming standards. In the field of quality control it is necessary to measure at higher accuracy than the specified regulations. Variability of the human eye cannot meet the higher standards of accuracy and repeatability to evaluate headlamp beam vertical alignment; therefore, it is necessary to evaluate headlamp alignment with electro-optical instruments. In order to meet both quality and liability issues, it has become necessary to accurately measure headlamp alignment traceable to the U.S. National Institute of Standards and Technology (NIST).
By 1999 the U.S. vehicle producers began significant introduction of headlamp arc lamps in their products. In so doing quality control for headlamp aiming, also known as “headlamp audit”, became a prime concern at Ford Motor Company. Early headlamp audit equipment at Ford used Adroit Engineering beam sensors without baffling to eliminate spillover between left and right vehicle beams. This purposely created a need for the audit operator/driver to exit the vehicle and sequentially stand in front of each lamp while observing the audited position of the opposite lamp. Thereby variation of driver body weight was eliminated from the production statistical process control record.
To accomplish the foregoing this invention eliminates stray light sensor interference by introduction of sensor baffling. Having the driver exit the vehicle is still accomplished by a requirement to manually activate software recording of data from a position near the smart sensors.